1. Field of the Invention
The present invention relates to a method of welding a plurality of members to manufacture a three-dimensional structure and an apparatus for use in such a method when a plurality of members are connected to be formed into a three-dimensional structure.
2. Description of the Related Art
Generally, for manufacturing a three-dimensional structure(for example, a tail tube of a gas turbine combustor), a plurality of members are connected with each other by welding to form a three-dimensional structure. They are welded by gas shielded arc welding using shield gas(TIG welding, MAG welding, MIG welding, electro-gas arc welding), plasma welding, and laser beam welding, etc.
By the way, when connecting a plurality of members by TIG welding, generally the welding has been carried out by hand. In the case of hand welding, the quality of the welded part is various depending on the skill of the worker, since the location, width etc. of the welding position is different according to the line of welding(welding line). As a result, the quality of the welded structure is unstable.
For this reason, the welding by the use of carbon dioxide(CO2) laser welding has been adopted in which the position to be welded is indicated by irradiating the position by a laser spot light and welding is done taking the laser spot light as a guide.
However, when the method of welding the position indicated by the laser spot light as described above is applied for welding a plurality of members to form a three-dimensional structure, there may occur the case the laser spot light deviate from the position to be welded depending on the position of the laser light emission and the irradiated position. For this reason, when welding was carried out on the position irradiated by the laser spot light, faulty welding such as the deviation from the weld line to be welded occurred in many cases, resulting in the necessity of repairing faulty weld.
Particularly, at the production of a three-dimensional structure by combining a plurality of members, plastically deformed member themselves may be deviated a little from the design drawing(designated shape). Faulty welding tends to occur inevitably when such members are combined and welded even when welding position is irradiated by a laser spot light, for the laser spot light may often deviate from the position to be welded.
To eliminate the disadvantage like this, a teaching method in YAG laser beam machine is disclosed in Japanese Patent Application Publication No. 2000-263272, in which the teaching is executed beforehand three-dimensional laser machining is carried out by irradiating the work with the YAG laser light which is emitted from a laser oscillator, transmitted via a fiber-optic cable, and radiated onto the work through the light-gathering lens provided in the laser machining head, characterized in that, the positions in the direction of height of a plurality of teaching points on the work are detected by the height detector provided in the laser machining head, a light for measurement emitted from a light source head which is provided outside the laser machining head and is set beforehand to pass the focussed position of the YAG laser light, irradiates the plurality of teaching points one after another, each reflected light from the work is photographed by a photographing means to represent on a display, the focussed position of the YAG laser light is detected by moving the coordinates of the reflected image on the display back-and-forth and side-to-side to allow the image coincide with the focussed position of the YAG laser light, a master job is produced by automatically storing the three-dimension data consisting of the position in back-and-forth and side-to-side direction and the height position of each of the teaching points by an image processing apparatus, and for ordinary job a corrected job for each work is produced by automatic analysis and correction of said master job at the same points as those of said master job on the basis of the three-dimension data of the plurality of the teaching points of said master job in said processing apparatus as necessary.
According to the invention, the three-dimension data consisting of back-and-forth and side-to-side position and height position is determined automatically for each of the plurality of teaching points by the image processing apparatus, analyzed, checked, and corrected to be reflected in the program, so that teaching accuracy is improved, stable laser machining is performed, and further when the work is changed, the check and correction are automatically executed by the image processing apparatus. Therefore, the checking and correcting process of the teaching points by the worker when the work is changed is eliminated, which eliminates the needs for workers burden and time, resulting in stable small lot production of three-dimensional structure without using jigs of high accuracy and highly accurate component members.
However, in the prior art like this, operation is needed for making the light image coincide with the focussed position of the YAG laser light by moving the light image back-and-forth and side-to-side on the display after the height position of each of the plurality of teaching points is detected in order to obtain the three-dimension data consisting of back-and-forth and side-to-side position and height position. Therefore that teaching operation becomes complicated.